1. Technical Field
The present invention relates to an image reading apparatus and, more particularly, to a technology for detecting a predetermined pattern that defines a reference position that specifies a reading position in the image reading apparatus.
2. Related Art
Scanners are widely used as image reading apparatuses that optically read a reading object with an image sensor and then generate image data on the basis of the read result. In the existing art, each of the scanners uses a position sensor in order to determine a reading position in the scanner. In addition, another method has been known in which a reading position is determined in such a manner that, for example, a predetermined pattern formed of a black region and a white region is provided for the scanner, an image of the pattern is detected from read image data and then the position of the detected image of the pattern is set as a reference position (which is, for example, described in JP-A-2000-113162).
In the technology described in JP-A-2000-113162, a carriage is configured to be located around a home position when power is turned on, and the position of a predetermined pattern is also specified in connection with the home position. However, in the scanner, it is conceivable that, for example, as in the case immediately after abnormal end, the carriage may be located at a position different from the home position when power is turned on. In such a case, because the position of a predetermined pattern is not specified, the process to search and detect a predetermined pattern should be performed. The detection of a predetermined pattern is preferably performed quickly and reliably.